#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <vector>
using namespace std;
class Solution {

    vector<int>s;
public:
    int pivotIndex(vector<int>& nums) {
        int n = nums.size();
        vector<int>f(n); vector<int>g(n);
        for (int i = 1; i < n; i++) f[i] = f[i - 1] + nums[i - 1];
        for (int i = n - 2; i >= 0; i--)g[i] = g[i + 1] + nums[i + 1];
        for (int i = 0; i < n; i++)
            if (f[i] == g[i]) return i;
        return -1;
    }
};

int main() {
    Solution sol;
    std::vector<int> nums = { 1, 7, 3, 6, 5, 6 };
    std::cout << sol.pivotIndex(nums) << std::endl;
    return 0;
}